1. Field of the Invention
The present invention relates to window glass for vehicle, having an antenna that utilizes a conductive film provided on a glass plate, and to the antenna utilizing the conductive film.
2. Description of the Related Art
FIG. 1 is a cross sectional view illustrating window glass for vehicle, having a conductive film 3 and an intermediate film 4 interposed between glass plates 1 and 2. In FIG. 1, an arrow D1 indicates a vehicle exterior side, and an arrow D2 indicates a vehicle interior side. Conventionally, in a case in which an antenna conductor 5 for receiving radio waves is formed on the vehicle interior side D2 of the glass plate 2 of the laminated glass, the radio waves arriving from the vehicle exterior side D1 may be blocked by the conductive film 3, and it may be difficult to sufficiently obtain a reception characteristic required of the antenna conductor 5.
In order to eliminate such inconvenience, known window glass may have an antenna function by utilizing a conductive film (for example, refer to Japanese Laid-Open Patent Publications No. 6-45817, No. 9-175166, and No. 2000-59123, and U.S. Pat. No. 5,012,255).
The Japanese Laid-Open Patent Publications No. 6-45817, No. 9-175166, and the U.S. Pat. No. 5,012,255 propose a slot antenna that utilizes a slot between the conductive film and a flange of a vehicle body to which the glass plate is fixed. In the case of the slot antenna that utilizes the slot between the conductive film and the flange of the vehicle body, the size of the slot is determined for each vehicle model, and it is difficult to cause resonance at a predetermined frequency, specifically, in order to receive radio waves in a high frequency band. Further, in order to receive radio waves in a high frequency band, a positional relationship of the flange and the conductive film needs to be accurately controlled. However, because there are differences among individual glass plates and the glass plate is fixed to the flange of the vehicle body by an adhesive, various errors may be generated in the adhesive thickness, the fixing position of the glass plate with respect to the flange, and the like. Accordingly, there is a problem in that it is difficult to form slots of identical sizes in mass production.
In addition, when a slot is provided in the conductive film in addition to the slot between the conductive film and the flange of the vehicle body as in the case of the U.S. Pat. No. 5,012,255, the effects of the conductive film may deteriorate when the additional slot is large, and there is a problem in that, when the glass plate is bent and formed by heating, a large heat distribution is generated on the glass plate depending on the existence of the conductive film, to thereby deteriorate the forming accuracy.